Method and apparatus for manufacturing a load bearing structural element having special internal atmospheric conditions

ABSTRACT

The invention comprises a method for manufacturing a load-bearing structural element, and a housing for such manufacture. The method includes positioning outer shell assemblies in the housing to form a hollow space, and positioning honeycomb plates and a central support assembly within the outer shells. The outer shell assemblies are thereafter forced toward each other whereby the edges of the plates are firmly pressed against the adjacent surfaces of the assemblies. The plates and shell assemblies are rigidly interconnected by welding, with the atmospheric conditions in the hollow space being controlled as desired. The housing includes means to initially space the components in the housing prior to pressing and welding.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division, of application Ser. No. 533,453, filed Dec. 16,1974, now U.S. Pat. No. 4,090,340, which in turn is a continuationin-part of Appln. Ser. No. 502,094, filed Aug. 30, 1974, now abandoned.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a structural element and moreparticularly to a load-bearing structural element useful, for instance,as wall element, for structures, supports, bridges, vehicles, andothers.

(2) Description of the Prior Art

Structural elements which consist of two or more structural shells orpanels of at least one sealing packing lying between the edges of theshells or panels, and a cavity hermetically enclosed by them have beendescribed heretofore. In the cavity of said elements pressing means, forinstance, honeycomb plates with interposed solid plates, for instance,metal plates and associated sealing plates, for instance, foam-plasticplates which can be covered with vapor-proof sheets, for instance,aluminum foils, are provided and at least one of the structural shellsor panels is arranged so that it can shift its position flexibly, or canbe bent, for instance, concavely against the seal, and a vacuum isproduced within the cavity.

As a result of the elimination of air counterpressure or back pressurewithin the structural element, the external air pressure causes at leastbending or sagging of the flexible structural shells or panels and/or inparticular a change in place of the structural shells in directiontowards each other by compression of the seal and the cavity inserts. Asa result of said atmospheric pressure, the inserts in the cavity,particularly the honeycomb webs or straps, are placed under tension andpress with this force against the interposed metal plates and the innersides of the structural shells. This results in increased resistance tobending of the inner plates and intermediate panels or sheets supportedin this manner, as well as of the outer structural shells or panels, inthe event that they are acted on by load in the direction of theirplanes. In the case of a vacuum, this amounts, perpendicular to theouter shells or panels and the honeycomb plates on the surfaces of themetal plates arranged in the cavity and other intermediate plates, toabout 10 tons per sq.m.

This atmospheric pressure is of randomly caused order of magnitude. Itis determined by the gravitational force of the earth on the atmosphere,the composition of the air as a mixed gas, and the height of theatmosphere.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide a structuralelement, preferably of metal or plastic, and in particular aload-bearing structural element, the use of which is of great advantageespecially in the following fields:

Construction engineering, vault construction, dome construction, tunnelconstruction, underground installations, underwater structures,formation of supports, piles, girders, frameworks, masts, chimneys, alsoin the form of load-bearing pipes and pressure pipes, furthermore bridgeconstruction, vehicle construction, for instance of land, sea, air, andspace vehicles, container construction, and as load-bearing foundationconstruction; also for machines and objects, as well as for supportingwalls, water-retaining dams, breakwaters, and the like. This enumerationis not exhaustive.

A further object of the invention is to provide improved heat- and soundinsulation in the load-bearing structural element. Heretofore, suchsound insulation was achieved in the art by absorption of theoscillation energy of the sound rays or waves. This requiresconsiderable masses of structural material per square unit for the wall.The absorption can be increased by combination or by compositeconstruction with soft, porous materials which are not capable ofoscillating. The structural material itself can consist of suchcombinations of material which have an increased absorbing effect onsound oscillation. Another object of the present invention is to providea process of manufacturing such a structural element in a simple andeffective manner.

Still another object of the present invention is to provide an apparatusfor manufacturing such a structural element.

The structural element according to the present invention is composed oftwo or more structural shells or plates which enclose or envelope atleast one cavity or hollow space. If required, suitable packings orborder strips are provided at least between the edges or bordering partsof said shells or plates. In the hollow space or spaces there arearranged propping, reinforcing, or bracing means, for instance,honeycomb plates or spacing strips or bars, preferably with interposedsolid plates, for instance, metal plates. If necessary, sealing ortightening plates, for instance, plastic foam plates, which arepreferably covered with vapor-tight foils, for instance, of aluminum,are provided. At least one of the structural shells is movably arrangedso that it can change its position and/or is flexible, for instance,concavely bent or deflected. A vacuum or a pressure which is lower thanthe pressure acting from the outside on the propped or supported shells,is produced in the hollow space or cavity.

As a result of the elimination of the atmospheric pressure within thestructural element, the external air pressure causes at least bending orsagging of the flexible structural shells or panels and/or in particulara change in place of the structural shells in direction towards eachother by compression of the seal and/or the cavity inserts. As a resultof said atmospheric pressure, the inserts in the cavity, particularlythe propping or supporting means, the honeycomb webs or straps, or theshells of the cavities are placed under tension and press with thiscounter force against the interposed metal plates and the inner sides ofthe structural shells. This results in increased resistance to bendingof the inner plates and intermediate panels or sheets supported in thismanner, as well as of the outer structural shells or panels, in theevent that they are acted on by load in the direction of their planes.In the case of a vacuum, this amounts, perpendicular to the outer shellsor panels and the honeycomb plates on the surfaces of the metal platesarranged in the cavity and other intermediate plates, to about 10 tonsper sq. m.

The preferably concavely bent or deflected structural shells or panelsare kept from each other at their border parts by means of packings and,if required, of other means at a distance which is greater than thedistance produced by the action of tightening screws or clamp bolts inthe central parts of the shell or panel surfaces. Said shells or panelshave the tendency, when subjected to increased load, to further decreasetheir distance from each other in the direction parallel to their planesor surfaces. As a result thereof a correspondingly increased countertension of the propping, bracing or supporting means, for instance, ofthe honeycomb plates, of the walls of the cavities or chambers, of thespacing strips, and thus a corresponding reinforcement of the localbracing shells or panels and of the plates provided in the cavity orhollow space is achieved.

This atmospheric pressure is of randomly caused order of magnitude. Itis determined by the gravitational force of the earth on the atmosphere,the composition of the air as a mixed gas, and the height of theatmosphere.

Structural shells of sheet metal which contain an elastic plastic layer,particularly a highly viscous thermoplastic material, for instance vinylacetate copolymers, or foils of vinyl copolymers in two layers eachbetween said structural shells to thus form a sandwich composite plateare known in the art. The oscillation energy in such plates is convertedin said layers into heat due to tangential stress or shearing stress. Asa result thereof the prerequisite for a radiation of the sound towardsthe interior is eliminated to a considerable extent before the innercomposite sheet metal is reached.

The sound transmission level is considerably decreased and the bendingstrength or rigidity is increased. Reduction of the sound energy asachieved by this manner of sound-proofing, however, is only achieved upto 35 decibels. This is insufficient to achieve the required soundproofing effect.

In accordance with the present invention, the sound insulation isachieved almost without absorption of the oscillation by reflection ofoscillation. At least one layer and preferably several layers ofhoneycombed plates, preferably consisting of insulating material, forexample, hardened Kraft paper or cardboard or plastic are employed inorder to acoustically and thermally insulate the structural element in alightweight construction manner. For this purpose the honeycombed platesare provided with highly reflecting surfaces and are tightly sealed onboth sides with highly reflecting aluminum foils or the like. Eachindividual cell thus forms a reflecting chamber which is closed on allsides.

The present invention is based, among other features, on the concept toproduce the compressive forces as required independently of theabove-explained compressive force caused by the earth and thus to obtainpressure differences either with respect to a vacuum or with respect toa partial vacuum or some other lower degree of pressure. This isachieved according to the present invention by pressing alternatelyarranged local bearing, supporting, propping, or bracing plates, heatand/or sound insulating plates, honeycomb or grid plates with preferablynarrow ribs or bridges transversely to their principal plane or surface.For this purpose the hollow spaces or cavities of the structuralelements are evacuated before exposure to pressure action preferably inan evacuating housing. As a result thereof there is produced not only ahighly bending resistant or rigid structural element but also,especially on account of the still present but evacuated cavities orhollow spaces, a construction element which has an especially high soundand heat insulating capacity. In this connection the extraordinaryincrease in the action of the pressure by concentrating a given pressureforce on a few places of linear pressure contact is of considerableimportance for the pressure action on solid surfaces to be supported, byproviding, for instance, narrow, flexure-resistant, low honeycomb websof, for instance, steel, with honeycomb sizes which are relatively largeas compared with the webs or bridges of the webs. In this way the resultis achieved that the pressing force, instead of being transmitted fromone total surface to the other total surface, is corresponding to thehoneycomb structure- transferred only in honeycomb-like fashion linearlyto the surface to be supported. Said lines of contact constitute, forinstance, less than 1% of the total surface. The pressing force actsonly on these structured lines of contact which are distributed in anetwork-like fashion over the entire surface. If the structural shellsor panels are pressed together with a vacuum in the cavity, forinstance, with the atmospheric pressure of about 10 tons, then thelinear surface parts contacted directly in net-like manner by thehoneycomb webs, bridges or ribs and constituting about 1% of the totalsurface of the solid surface intermediate plate are pressed togetherwith a force of about 100×10 tons=1000 tons. The pressure of 1 atm.gauge, if necessary, can be increased as desired by air-pressure pumpsand apparatus. With a pressure, for instance, of 100 atmospheres, thereis obtained an increase in pressure to 100,000 tons of pressure, withrespect to the linear net-like contact points on the shells andsupporting plates which are to be pressed. The load-carrying capacity ofthe supporting plates pressed in this manner is of about the same valueinsofar as the intermediate spaces or portions (areas) not contacted bythe honeycomb webs, bridges, or ribs are sufficiently resistant tobending under said load.

The resistance to bending of each individual portion (area) of thesurfaces is caused by the resistance to bending of the supporting plateitself, with due consideration of the size of the partial surface.

Since, however, each individual partial surface takes up a relativelysmall percentage of the total surface, their resistance to bending iscorrespondingly high. Thus the honeycomb (cell, chamber) widths can bemaintained approximately large enough so that the partial surfaces ofthe supporting plates which are defined by them provide a resistance tobending as required in each case. In this way it is possible to increasethe ratio of the net-like contact by means of the honeycomb webs,bridges, or ribs as compared with the total area of the inner supportingplate for maximum concentration of the pressure force on the smallestpossible proportion of the surface of the plates to be supported. On theother hand, the resistance to bending of the load carrying plates to besupported can be increased in advance by developing them as compositeplates in sandwich or multiple compound fashion by the use of plasticmaterial of the highest bending power, and particularly by the use ofsolid but preferably still elastic plastic material specifically suitedtherefor as center as core of the composite structure, by which thethrust forces are prevented from loosening the outer cover plates of thecomposite plates.

There can thus be obtained honeycomb widths which produce a maximummultiplication of the pressing forces by even further concentration on afew honeycomb webs, bridges, or ribs or on pressing surfaces taken up bythem.

Another possibility of increasing the resistance to bending resides inthe development of structural shapes, for instance, of trapezoidalprofiles or channels in compound construction with solid plasticmaterials and in the combination of such composite profiles or shapeswith each other. They can be covered by flat composite plates, having areal contact with the pressing means, for instance, the honeycomb platesand can be firmly connected or joined thereto, for instance, by glueingor welding.

It is advisable to support the honeycomb bridges or ribs, for instance,by partially introducing foam into the honeycomb in situ by means offirmly adhering rigid foam. Evacuation of the cavities is notnecessarity required. The decisive factor is the pressure differencebetween the pressures in adjacent cavities which are separatedhermetically from one another by a movable structural shell or plate.

In the same way as in the case of vacuum or reduced pressure, it isnecessary, for reasons of safety, also to divide the cavity in which apressure greater than atmospheric pressure is present, into a largenumber of partial spaces, for instance, by honeycombs or grids, so thatthey are closed off hermetically from each other and from the entirecavity. In case of a partial destruction of the outer parts of thecavity and of the corresponding inner parts, the parts which are stillnot destroyed can still exert excess pressure without change.Furthermore, by appropriate subdivision, the effect of possible damagecan be restricted to a minimum. Since the excess pressure tends toincrease the volume taken up, the hermetic closing off of such honeycombspaces which are under pressure is only possible if, as the result of aneven greater outer pressure, the sealing plates arranged on the insidefor sealing off of the honeycombs are pressed from the outside into thehoneycombs by said correspondingly higher pressure and if said state orcondition is maintained.

The movable structural shells or panels of displaceable positiontherefore must be locked in this condition of their smallest distancefrom each other in order to definitely maintain the compressive stressproduced by the position assumed by them for an unlimited period oftime. For this purpose, various means can be provided which will bedescribed hereinafter.

In my prior application Ser. No. 502,094, filed Aug. 30, 1974, aconstruction element is described which consists of two or more buildingshells, at least one sealing unit positioned between the shell edges,and a hollow space hermetically enclosed thereby, wherein means to bepressed on e.g. honeycomb plates, with intermediate fixed plates,complete the construction element.

In accordance with another embodiment of the present invention, there isfurther provided a welding of the honeycomb plates, grid plates and/orother plates which constitute the core (or cores) between theload-bearing building shells and/or building plates, together with theadjacent surfaces of the said plates to a fixed, airtight and vaportight unit, preferably in a vacuum chamber, for instance, under a realpressure by means of a welding current, especially a capacitor-impulsewelding current, (for welding metals) or a high frequency current (forwelding plastics). For the purpose of such welding, the building shellsor building plates, as well as the core-forming plates are preferably ofsteel or aluminium or of plastic material. The honeycomb plates or gridplates may be made, for instance, of trapezoid or undulating bands, inwhich structure they support further bands which extend between thesebands rectilinearly and are somewhat wider than the honeycomb-forming orgrid-forming shaped bands and overlap toward both sides, e.g., by about1 mm. Due to such structure, only these somewhat higher positionedintermediate bands come in contact with the building shell surfaceduring the welding of the honeycomb plates, grid plates, or the like.The air can first be evacuated by way of these air gaps, or a positiveair pressure can be established in the honeycombs, chambers, cells, orthe like.

The welding can be carried out e.g., as resistance welding or aselectronic welding (electric arc welding), or as combinedresistance-electronic welding, or as high frequency welding forplastics. In the case of electronic welding the electrons are ejectedfrom the cutting edges of the honeycomb bridges upon the metal surfacesof the adjacent metal building shells or metal building plates andthereby the parts to be welded together are melted-on and in this stateare pressed toward each other and thus welded together. By this welding,each individual honeycomb, chamber, cell, or the like is sealed towardthe outside in a vapor tight manner. In these hollow spaces there existsfor an unlimited period of time the air or gas pressure or a vacuumproduced in a prespecified manner in the hollow welding space.

In the electronic welding or the electric arc welding the optimumwelding duration can be determined by the greater height of the, forinstance, rectilinear intermediate bands or the honeycombs or the like.This welding duration corresponds then to the time required for meltingaway the overlapping height of the inserted bands. For the purpose ofoptimum welding all other welding data must also be brought into anoptimum ratio thereto.

The honeycomb bridges, grid bridges, or the like, may, for the purposeof forming airgaps and thus for allowing evacuation of the cells orchambers, also be shaped in another manner; thus they can be provided,e.g., with teeth at the cutting edges. Furthermore, the metal surfacesof the adjacent building shell can be provided with, for instance,linear stiffening corrugations which cause formation of airgaps untilthe stiffening corrugations have been welded together, at the points ofcontact with the honeycomb or grid bridges, or the like, in such amanner that the entirety of the bridges likewise comes in contact, andis welded together, with the adjacent building shell surfaces and witheach other. Thereby all honeycombs, chambers, cells, or the like canfirst be evacuated and then be sealed off in vaportight manner. Thehoneycombs, grids, or the like, and likewise the surfaces of thebuilding shells may consist, as mentioned hereinabove, of plasticmaterials and be welded together, by high frequency. This must takeplace likewise under optimum conditions, established in the weldingspace.

Such parts, firmly connected with each other to composite plates may,depending on suitability, be provided in multiple numbers and evacuated,by arranging the honeycombs or grid plates on both sides at the surfacesof the building shells or plates and the inserts. Excess pressurechambers may be assigned at one or both sides to such composite plateunits, which excess pressure chambers serve to increase the bendingstrength of the load-bearing parts of the composite plates whereby theforce component acts vertically to the surfaces of the shells andplates.

The combination may also take place in such a manner that the excesspressure chamber is arranged between two composite plate units. By meansof the excess pressure chambers the honeycombs or grid bridges are, incorrespondence to the excess pressure exerted upon the building shellsor covering plates thereof, put under tension which they in turn exertas a counteracting force on the load-bearing building shells or buildingwith their inserts, thus increasing the bending strength thereofcorrespondingly. It is also feasible to place in front and/or behind theparts concerned, between a flexible internal building shell or buildingplate which is flexible or of variable position and a composite unitelastic layers, e.g. rubber plates, plastic foam material plates. Theexpansive force of the excess pressure can be limited by providingtightening screws and clamp bolts to its spatially intended extent.Since the horizontal force component derived from the force of the loadamounts to only a small fraction of the load, it is possible to increaseextraordinarily by means of either gaseous or liquid or solid substancesfilled into the excess pressure chambers the bending strength and as aresult thereof the breaking or ultimate strength in combination withhoneycomb ribs or chamber or cell walls by applying such a supportingexcess pressure. Porous layers are to be made universally airtight andvaportight, e.g., by means of metal foils or polyethylene foils and orsheet metals. If required, there are to be interposed preferably elasticlayers to yield composite structures. The excess pressure produced inthe construction element in one or more excess pressure chambers must beintroduced in the form of tensioning means into the supporting shells ofthe construction element, preferably by way of the bridges of the corebuilding material.

The core, especially the plates with honeycombs, grids, or the like arealso constructed as load-bearing plates. This can be done in such amanner that, especially in vertical direction, the parts that form thecore plates are all constructed as load-bearing plates and are deformedspatially, for instance, in a corresponding manner as vertical(upright), trapezoid or undulating load-bearing plates which inhorizontal direction are subdivided, in an airtight and vaportight,stationary manner, into individual chambers, cells, or the like. Suchtrapezoid plates may, with their horizontal or their transversesubdivisions, be rigidly connected with adjacent plane plates or withplates which are likewise constructed as composite plates, for instance,by welding and form an entire composite unit. They may also be connectedin a manner of variable position, with adjacent pressure chambers andmay be supported thereby so as to be in elevated fixed position. Inorder to increase the breaking strength of such shaped vertical coreplates they may be crosswise connected, for instance, with horizontal,trapezoid plates, e.g., by welding and/or cementing and may carrybetween them separating metal sheets by which the chambers, cells, orthe like thus formed are sealed in an airtight manner.

Such core elements may also, individually or as a unit, universally besealed toward the outside by cementing and/or welding in an airtight andvaportight manner, e.g., by metal or plastic material parts and/orlayers. Many shapes and combinations are possible which may serve thesame effect.

Finally, it is also possible to provide the chambers, cells, honeycombs,or the like, of such composite plates with a higher pressure than thatof atmospheric pressure and to use, e.g., flexible, welded-on coverplates as an airtight seal of such hollow spaces and to exert, by meansof the flexibility thereof, a pressure upon adjacent, evacuatedchambers, preferably rigidly connected with the said cover, and arrangede.g. crosswise thereto, so as to increase the bending strength of thelatter. For this purpose it is suitable to give a relatively large sizeto the excess pressure chambers, honeycombs, or cells, in order toenable the free surfaces limited by the bridges to present sufficientflexibility for exerting a pressure upon adjacent honeycomb bridges,cell or chamber bridges, which in turn can support the load-bearingplates or parts thereof, as well as the, e.g., trapezoid core plates, inan improved bending resistant manner. The bridges of the honeycombs,cells, chambers, or the like can be kept in any suitable bending-proofthickness and height, depending on requirements due to the selectedmaterial, or they may be reinforced by material combination or compoundarrangement and/or fillings. The edges of these bridges may alsopreferably be constructed as sharp as a knife and/or they may be toothedor serrated, in order to make possible resistance and/or electronic(electric arc) and/or high frequency welding.

The larger the partial surfaces limited by the honeycombs, cells,bridges, of the cover plates or the load-bearing building shell happensto be, the stronger, at equal pressure, must be the bridges, and themore favorable can be, on the other hand, the ratio between thecontacted surface areas and the total surface of the building shell, andthus the concentration of the pressure upon the surface portions of theadjacent load-bearing shells or compound plates. The transversesubdivisions, e.g., of the trapezoid surfaces for the formation ofchambers may be of any suitable material, e.g., metal, plastic material,rubber. Their mutual airtight seal may also be produced, in addition, bythe pressure of the adjacent cover plate and by thus producedcompression or by welding.

The composite building element can also be made without the sealing, andthen this element can be introduced into the hollow space of a largerbuilding element. The building plates or shells of the internal buildingelement can therefore be connected with those of the external element,e.g., by cementing plastic material foils or cementing layers. Then thehollow space which may still remain between the internal and theexternal building element can separately be evacuated. The breakingstrength of such a building element is assured by the internal buildingelement.

In accordance with a further aspect of the invention, intermediatelayers are provided between an insulating group and the succeedinginsulating group, for instance, of the same type between any twoaluminum foils. Such intermediate layers are composed particularly ofinsulating material, for instance, insulating plates of plastic foam,glass fibers, felted cardboard, and/or also metal sheets.

The structural element can be made up and assembled in a room, the airof which is dehydrated to such an extent that condensation of watervapor present in the air in the cells is excluded after the insulatinggroups have been produced. This is of great importance because even avery slight precipitate of water upon the reflecting aluminum surfacesof the cell will almost completely nullify or cancel their reflectivepower for heat rays.

The structural element can also be assembled in a room in which the airis evacuated. Since the air in the structural element, on evacuating thesurrounding space, tends to escape outwardly from the cells underatmospheric pressure, i.e. with a force of 10 000 kg./sq.m., thehorizontally superposed layers of such a structural element are slightlylifted until the weight per sq.m. is equal to the residual air pressureremaining in the structural element. If, for instance, this weight is 20kg./sq.m. above the resting lower structural shell, this corresponds to1/500 of the atmospheric pressure which is previously [initially]present therein (10 000 kg.). The residual pressure at which thesuperposed layers settle or sag upon each other, thereby mutuallysealing each other, thus amounts to only 1/500 of an atmosphere (=1000g. divided by 500, i.e. 2 g. per sq.cm.). If the air is subsequentlyagain introduced in such a space which can be evacuated, the atmospherepresses from the outside with a force of 10,000 kg./sq.m. upon the upperwall shell and thus presses said shell against a circular packing sothat the structural element is air-tightly sealed on all sides in theabove-described evacuated state. Thereafter screws which have alreadybeen loosely inserted at an earlier time, can be tightened preferablyuntil a predetermined distance is achieved. As a result thereof thefollowing effect is obtained:

The structural shells can abut not at all or only slightly against theinsulating groups or the panel of the hollow space depending upon thedimensioning of their marginal angle and/or their packings. In this casethe residual oscillations into which the composite sheet metal is set,are only to a slight extent or not at all transmitted to the adjoininglayers as sound conducted through solids. Between the composite sheetmetal or, respectively, the aluminum foil fastened thereon and theadditional aluminum foil closing the honeycombed cells, there can bearranged sound-proofing intermediate layers, for instance, a fiberglassmat or web or a plastic foam plate as above described. Theseintermediate layers can take up partly in an absorbing manner the soundoscillations. If the honeycomb cells are completely evacuated, no soundoscillations can be transmitted through the free space. Sound can bepropagated only via matter which can be set in periodic oscillations.The honeycomb ribs remain as bridges for sound conducted through solidsfor a further transmission of the sound. Assuming that the firstinsulating group or, respectively, the honeycomb plate has taken overthe oscillations via the ribs, these ribs can be placed at the oppositeside vertically against sound-proofing plate material, as stated above.In this manner a further part of the oscillation energy is againconverted into heat by the damping effect. This can be continued asfrequently as desired so that total conversion of the oscillation energytoward the opposite structural shell is achieved with certainty. In casethe structural shell could still be caused to oscillate because, forinstance, only one insulating group is arranged therebetween, suchoscillation would be converted into heat via the successive cavity whichis limited with respect to the structural shells by an inner wall of anydesired material. In addition thereto, said cavity can be providedeither in the same manner as the cavity or, for instance, with otherspacer means.

In the aforesaid example the structural shells can be formed more orless flexible or resistant to bending depending upon the requirements.As a result of the vacuum in the structural element, there occurs aconcave more or less pronounced bending of the structural shells in thedirection towards each other. Due thereto the shells are under a statictension. This concave tension renders difficult the formation oftransverse waves due to the correspondingly high inherent frequencieswhich are produced by the degree of tension. These inherent frequenciesabsorb only those oscillations from the sound or frequency mixture, forinstance of the street noise which correspond to their fundamentaloscillation and to overtone oscillations which are in an integralproportion therewith. Thus a selective resonance occurs while all otheroscillations energies are reflected from the outer surface of thestructural shell as from a hard shell wall. Thus absorption of all soundradiations or emissions which are not in resonance is not achieved. Thusthe greatest part of the sound energy of mixed frequencies is preventedfrom entering the structural element. Regarding the conversion of theremaining resonance energy into heat, there applies what has beenexplained hereinabove.

In a further embodiment, the structural shells or structural plates canbe made flexible or can be dimensioned correspondingly and can firmlypress the insulating groups arranged therebetween by means of theexternal atmospheric pressure. This is of special importance withrespect to load-bearing structural elements. In this case, theinsulating groups serve at the same time as supporting cores. Bypressing the honeycomb ribs into the insulating layers arranged betweenaluminum foils, for instance, compressible plastic foam plates, thefoils are pressed in a convex manner with tension into the cells likecushions or padding. The pressure of the honeycomb ribs against thecomposite metal sheets upon the lines of contact is a multiple of theforce which results from the pressure of the structural shells (10,000kg. per square meter) by reducing the lines of contact to thecorresponding structure of the honeycomb ribs which are distributed in apolygonal net-like manner over the inner surfaces of the structuralshells, for instance, with a contact of only 4% per square meter of theinner surface. The honeycomb ribs thus exert 25 times the counterpressure upon the lines of contact. This net-like pressing structuredevelops oscillation common or nodal lines on the structural shells.Thus the structural shell can absorb and emit only oscillations as theycorrespond to the natural or inherent frequency of such a small partialsurface corresponding to the boundary lines of the cells. These naturalor inherent frequencies are so high that they are beyond the audiblelimit. As a result thereof all those frequencies which are containedwithin the sound mixture of the noice acting from the outside, arecompletely reflected. The honeycomb ribs which form the common or nodallines are also not able to oscillate because the nodal lines are notoscillating. As a result thereof this possibility of transmitting soundenergy from the one structural shell to the opposite structural shell isalso excluded.

A further variant consists in the feature that, as mentionedhereinabove, the cells are filled with dried air. In this case partialreflection of the energy of the sound conducted through solids can takeplace as aerial sound between the aluminum foils closing the cells. Thisreflection encounters a high interfacial resistance due to thedifference in density of the two media (metal-air). Its magnitude isdetermined by the foil as metal in the present case. As has already beenexplained, the compressible insulating plates which carry the aluminumfoils are pressed in a convex manner under tension into the cellsspaces. If these metal foils were free at both sides, they would possessa high inherent frequency and thus a corresponding selective resonance.Because, when pre-stamping or pre-pressing of the aluminum foil into thecell filled with air, the one surface of the foil, namely that surfacewith which the aluminum foil rests against the insulating plate, ispre-pressed and tensioned by the latter, no natural oscillationfrequency can occur. This means that said metal foil cannot transmit thesound absorbed by it to the air layer in the absence of any oscillationpossibility. The sound energy which acts from the insulating plate uponthe convex pre-pressed and thus tensioned inner side of the aluminumfoil is almost completely reflected from the latter as from anon-sound-absorbing wall.

It is advantageous to make the insulating plate of plastic foam withclosed pores. The sound intensity, i.e. the magnitude of amplitudes isat least diminished.

The aluminum foils which rest on both sides against said insulatingplates and enclose them project the sound oscillations which partly havepassed therethrough, into the porous cells of the plastic material withclosed pores. At the boundary surface between the porous wall and theair in the pores there is effected at least partly complete reflectiondepending upon the position of the angle, and partly penetration intothe air-filled pores. Circulation takes place in said poresapproximately corresponding to a polygon inscribed in a circle. As soonas the sound oscillations leave their track or course, they arereflected by means of the aluminum foils which surround the foam plateon all sides, again from said foils as in a complete mirror chambercorresponding to the honeycomb cells reflecting all over from one innersurface of the mirror-like adjoining foil to the other foil. Therebypartly stationary waves at the same frequency and partly interferencesand furthermore partly extinctions of oscillation are produced byoscillations which move in the same direction in phase opposition at thesame frequency. The oscillation energy thus is almost completelyenclosed and accumulated within the porous foam plate. When severalinsulating groups with such porous insulating plates enveloped byreflecting aluminum foils are provided, it is possible to convert theentire sound energy safely into heat. The amplitudes of suchoscillations are at least also in this case reduced to such an extentthat the sound level is below the range of audability. The honeycombribs with the aluminum foils or, respectively the insulating groups canbe pressed on both sides against the intermediate sheet metals. As aresult thereof there are formed on both sides very irregularlyintersecting common or nodal lines which sub-divide the entire surfaceof the intermediate sheet metals not only corresponding to the honeycombsurfaces, but also in a completely ungeometrical form corresponding tothe incidental position of the honeycomb ribs on the one or the otherside of the intermediate sheet metal. Thereby the intersecting pointsare under an especially high pressure and represent also completelyirregularly distributed nodal points. Development of inherentoscillations or, respectively, frequencies and of harmonic vibrations orovertones which are in a simple relation thereto, is almost completelyexcluded. The intermediate metal plates thus acquire the property ofnon-sound-absorbing heavy plates, a property which belonged heretoforeaccording to the state of the art only to very hard and at the same timemassive, very heavy and thick plates and walls. This property thus isimparted in the above mentioned manner even to thin sheet metals. At thesame time there can be increased in this manner the bending strength andthus the carrying capacity almost up to the yield point or flow limitcorresponding to the magnitude of the pressure which acts at any timevertically upon the surfaces of such a sheet metal on both sides.

The described manner of pressing against the surface whereby irregularcrossing over on both sides takes place can be evaluated so that thewidth of the cells, the partial surface of which, as has been explained,is further sub-divided by the nodal lines fromed from the other side,can now be made considerably larger. The contact pressure of thehoneycomb ribs renders possible to achieve increased bending strength ofthe intermediate sheet metal due to its concentration upon a diminishedtotal length of the lines of contact corresponding to the widemeshed netstructure or reticular structure. Production of a vacuum for generationof pressure of the wall shells upon the filling has already beendescribed. Assuming that the structural shells, or, respectively, thestructural plates are absolutely resistant to bending, for instance byproviding re-inforcing means, there could be exerted a uniform pressureof the structural shells upon the surface of the supporting coresarranged therebetween, especially via the bolts provided along the edgeparts.

It is possible to exert, by means of bolts, thousands of kilograms ofpressure per square centimeter. It is, of course, understood that suchbolts can be provided not only at the edge parts but also at any desiredplace from wall shell to wall shell preferably with the provision of aproper packing between the wall shells through which these bolts pass,thereby sealing it air-tightly.

Convex pressing of the porous foam intermediate plates enveloped withaluminum foils into the cells can be carried out also in the followingmanner: The insulating groups and intermediate plates are superposed inan assembling room provided with dry air and are compressed togetherwith each other and introduced in this manner between the structuralshells.

Production of a sub-atmospheric pressure or vacuum in the cells can beachieved in an evacuatable chamber whereafter the intermediate platesand the covering layers are pressed into each other in a convex mannerby means of devices to be operated from the outside.

The invention includes further variatons. The packings can be providedin the form of transverse or longitudinal strips or straps similar todistance pieces or spacers in a manner resistant to bending so that thestructural shells are kept at a pre-determined distance from each otherwhen tightening the bolts passing through these packings. Thesetransverse or longitudinal packings which are resistant to bending formnodal strips on the structural plates or shells. As a result thereofonly the intermediate surfaces between the nodal strips can oscillatewith respect to each other corresponding to their distance from eachother. The insulating groups with the honeycomb plates and the aluminumfoils closing them can be arranged at an optimum distance to the innersurfaces of the structural shells between the strips of packing withoutcontacting said inner surfaces. Thus they have only a thermal insulatingfunction if a vacuum exists.

If, however, air is present in the cavities of the structural element,then the conditions exist as they have been explained hereinabove. Theoscillations of the sound conducting through solids are reflected orradiated as sound conducted through air from the interior of thestructural shell within the range of the cavities between the packingsand they contact the aluminum foil which envelopes the insulating plate.As far as they penetrate into the insulating plate through the aluminumfoil, those processes take place as they have also been describedhereinabove. The same processes occur also in the honeycomb cells,reflecting all over.

With respect to pressing the insulating plates into the cells on bothsides in a convex manner, the depth of the cells must be keptcorrespondingly larger. While for thermal insulating a distance fromaluminum foil to aluminum foil of about 10 mm. is to be regarded asoptimum distance, the distance must be selected in the present case asof about 3 cm. to 4 cm. depending upon the width of the cells of thehoneycombs whereby a free distance of about 10 mm. between the convexarchings is to be maintained. The cells of the honeycomb plates are air-and vapor-tightly sealed by the reflecting foils and by the pressurewhich is exerted upon the structural shells, between which the honeycombplates and the load-bearing interposed composite plates are provided.They are pressed with tension into the cells by means of the elastic orat least deformable, for instance, plastic foam plates which arearranged on the back of the reflecting foils (aluminum foils). Due totheir tension they would possess, when flatly or planely positioned, aninherent frequency, i.e. a selective resonance on account of which allother frequencies or oscillations are reflected and thus cannotpenetrate as sound throughout the structural element. Anyway soundoscillations are not conducted through a vacuum because they aredependent on the presence of matter.

By pressing the honeycomb ribs against the inner surfaces of thestructural shells and against the interposed composite plates, theshells and the plates can also only oscillate with their inherentfrequencies which are dependent upon the size and shape of the honeycombcells through which these surfaces are sub-divided into correspondingareas or sections and thus can oscillate acoustically. There inherentfrequencies, however, are above the audible frequency range. Thereby itis to be taken into consideration that the inner surfaces of the shellspossess also a tensile stress when they are bent or deflected. Saidtensile stress would also cause selective resonance. The interposedcomposite plates are subdivided into irregular acoustic fields orsections by the honeycomb ribs being pressed thereon on both sideswhereby formation of nodal lines is encountered. Therefore, they cannotconduct audible oscillations. Oscillating membranes are prevented tooscillate by contacting them slightly. In order to achieve soundinsulation it is advantageous to select large cell diameters and todimension the height of the honeycomb ribs so that an optimum spacebetween opposite reflecting foils which are round or rounded undertesnion, exists inspite of the pressed rounding or camber of thetensioned reflecting foils.

Heat insulation results from the high degree of reflection (about 90%)of the aluminum foils and by excluding air convection due to evacuationof the cells. Of the heat energy which is absorbed by about 10% there isemitted towards the opposite side only about 10%, i.e., about 1% of theoriginal energy. Thus almost complete heat insulation is achieved byproviding foils or reflectors/reflecting means, especially reflectingplates in multiple arrangement.

Such a structural element is protected against any penetration of watervapor due to the vapor tightness of the metal foils, metal sheets andthe like as well as the shells. Any corrosion in the interior thus isexcluded.

It is evident that the task of improving the bending strength as well asheat and sound insulation while at the same time preventing corrosion,is solved by the present invention in a highly effective manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Various illustrative embodiments of the present invention are shown inthe drawings without, of course, limiting the same thereto. Therebyreference will be had to producing a vacuum or partial vacuum or toproducing excess pressure in the structural element by introduction intoan evacuation or pressure housing from which, after evacuation onproduction of excess pressure, the structural element is removed, aswell as to safety measures such as screwing together the parts of saidelement for maintaining said pressure conditions in the structuralelement.

In said drawings,

FIG. 1 is a vertical section through an evacuator housing with therequired additional appliances, said housing having placed therein thecomposite structural-element parts arranged vertically therein whichparts will be removed after evacuation and before use; said structuralelement being provided with a circumferentially arranged packing.

FIG. 2 is a vertical section through the right-hand portion of anevacuator housing showing the right hand parts of part of a compositestructural element introduced transiently horizontally in the housing onsupporting means for evacuation.

FIG. 3 is a cross section through a pressure housing with a compositestructural element arranged therein for producing excess pressure withinthe cavity.

FIG. 3a shows engagement means for connecting the structural-shellsurfaces which together with packings define a cavity of the compositestructural element, parts of which are under pressure.

FIG. 3b shows a bolt which is fastened on the inside of one of the twofacing structural shells or panels and which, in the condition in whichthe shells or panels are at the slightest distance apart is locked insaid position by pressure in the pressure housing with associatedmachines which effect screwing.

FIG. 4 is a modification of FIG. 1, showing the composite structuralelement parts rigidly horizontally connected, and

FIG. 5 is a modification of FIG. 3, showing the composite structuralelement rigidly secured vertically in the pressure housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows in cross section a pressure-resistant vacuum housing 1adapted to receive temporarily for evacuation a composite structuralelement in vertical arrangement of its individual parts and groups ofparts.

Housing 1 is closed on all sides, except for a front opening whichserves for the temporary introduction of the individual parts and groupsof parts of the composite structural element. The opening can then behermetically closed. Pipe 2 for establishing a vacuum or partial vacuumextends through the upper housing wall 1a, said pipe having an outletvalve 3 and a branch connecting it to an air pump. Pipe branch 4containing valve 5 serves for re-introducing air, so that the evacuatedstructural element can be removed for use in construction.

Compressed-air cylinders 6 having pistons and piston rods 7 are arrangedon side walls 1b and 1e. The piston rods are movable in airtight fashionthrough the walls and serve to actuate reciprocatable vertical pressureplates 8 on slide bottom 9 of housing 1.

The parts and groups of parts of the composite structural element arearranged symmetrically in the following manner within the evacuatinghousing 1a, 1b, 1c, 1d, and 1e only during evacuation and/or the actionof pressure.

The outer structural shells 10 are formed of composite platesconsisting, for instance, of two metal plates 10a having a solid andelastic plastic intermediate layer 10b, for instance, of polyethylene(sandwich shape). The inner sides of these composite plates 10 areconnected with boards 11 of compressible material, such as plastic foamboards, felt boards, rubber boards, or asbestos fiber boards, forinstance, by means of layers of adhesive. The free surface of theseboards or plates 11 can be coated with layer 12 which is preferablyimpervious to vapor. This layer can be, for instance, a metal foilpreferably of aluminum, a vapor-impervious plastic foil, preferably ofpolythylene a layer of plastic applied in liquid form, or the like.These parts form a compact single composite group.

Between said layer 12 and a following honeycomb plate 13 there is anopen air gap 14. The honeycomb plate 13 can consist of any suitablematerial, for instance, of metal, particularly steel or aluminum, or ofplastic, or of cardboard. Instead of a honeycomb plate, some otherpressure-resistant plate having suitable perforations andcorrespondingly remaining narrow webs can be used. This honeycomb plate13 is followed by another open air gap 15. In order to assure and/ormaintain a narrow air gap, compressible inserts 13a can be inserted inindividual honeycombs, protruding slightly towards both sides.Furthermore, there is provided a composite group consisting of a centralload-bearing supporting plate 16 in multiple composite formmetal-plastic-metal-plastic-metal (16a, b, c, d, and e) and on bothsides of said plate 16 and firmly applied thereto compressible plates orboards 17, corresponding to those described hereinabove with respect toboards 11, and coatings 18, corresponding to those described hereinabovewith respect to layer 12. All the above described parts are then againprovided in symmetrical sequence.

FIG. 1 shows a circumferentially arranged elastically compressiblepacking 20, for instance, of synthetic rubber, between the edge portionsof the two outer plates 10. The upper part of the curcumferentialpacking is provided with pipes 21 with valves 22 through which the airwhich is present at atmospheric pressure in the structural element canflow out into the evacuated vacuum space. On the other hand, no air canpass from outward to inward into the structural element. A pipe or ahose connecting the structural element with an evacuating device andextending outward through a wall of vacuum housing 1 in hermetic fashioncan also be provided. Packing 20 can consist of several layers,particularly of layers of different elasticity, for instance, formed intransverse direction. At least the upper part of the packing can beprovided with horizontally extending insert strips of rigid material totake up pressure, said strips being inserted, for instance, in recessesof the compressible packing. On both sides of the two outer structuralplates 10, the movable pressure plates 8 are provided as describedhereinabove. With these pressure plates, the structural shells or panelscan be replaced in vertical arrangement with respect to each otherwhereby the circumferential packing and the described inserts arecompressed. The air gaps 14, 15 which previously served for evacuatingthe air from out of the composite element are eliminated. Under the highpressure applied by pressure plates 8, the elastic inserts 13a areforced back. The plastic foam boards with their vapor-impervious surfacecoatings, for instance, aluminum foils, are pressed hermetically intothe honeycombs. In this way there is produced a firm connection betweenthe honeycombs and the plastic foam boards. When the two outer pressureplates have reached their end position, this is also at the same timethe predetermined end position of the outer structural shells and of theinserts compressed between them. If the air is then let into the vacuumhousing, the atmospheric pressure will exert its action. The structuralelement can then be removed from the vacuum housing and can be deliveredto the site of use.

As a result of eliminating the inner pressure of the air, the structuralshells are moved towards each other and thus press thepressure-resistant honeycombs against the surfaces of the bearingsupporting-composite 10a, 10b, and 16a, b, c, d, and e which thus,corresponding to said pressure, are held additionally inflexure-resistant fashion in vertical position. By the back-pressure ofequal value acting on the inner surface of the structural shells orpanels 10a, said structural shells or panels are also supported on bothsides in flexure-resistant manner in addition as load-bearing elements.As a result of pressing the narrow honeycomb ribs into the elasticallycompressible vapor-imperviously coated sealing plates of plastic foam 11and 17, each individual honeycomb is closed off in an air- andvapor-tight fashion. In this way the load-bearing, flexure-resistantcondition of the composite element is assured. Even in the event ofpartial destruction of a structural shell or panel or of the edge seal,the vacuum remains in all the uninjured honeycombs and thus there alsoremains the support for the load-bearing composite plates 10a, 10b, and16a, b, c, d and e. The packing 20 can therefore be completely dispensedwith. The honeycomb webs or ribs can in addition be connected byadhesive with the compressible means 11, 12, and 17, 18 which close offthe honeycomb openings. All composite groups and elements are combinedby the atmospheric pressure into a compact tension and shear-resistantcomposite unit of increased resistance to bending.

Supplementing the foregoing description, it may be pointed out that theindividual groups and individual elements within the structural elementcan be arranged in an asymmetrical fashion, for instance, from one sidetowards the other one, depending on varying requirements. Reasons offire protection may also make the provision of other structuralmaterials necessary.

Instead of providing merely one central group of load-bearing compositeplates, a plurality of such or similar groups consisting of, forinstance, vertically load-bearing composite elements and resilientplates connected firmly to them and inserted in the honeycombs can beprovided following each other at small intervals thus having a highload-bearing capacity.

The composite structural element can also be made without packing 20 andsuch an element can then be introduced into the cavity of another largerstructural element. The structural plates or shells of the innerstructural element can thus be connected with those of said other outerelement, for instance, by adhesive plastic foils or by layers ofadhesive. The hollow space which then still remains free between theinner structural element and the other outer structural element can thenbe evacuated individually. Assurance of the load-bearing strength ofsuch a structural element is then preferably provided by the innerstructural element.

FIG. 2 shows, in a vacuum housing 1, the assembly of such a structuralelement in horizontal arrangement of its parts 13 and groups of parts10a, 10b, 13, and 12, 11, 25a, 25b, 11, 12. Said structural elementconsists of two outer composite structural plates 10a and 10b, forinstance, of two metal sheets 10a with layers of plastic 10b arrangedtherebetween in composite fashion and consisting, for instance, ofpolyethylene. The inner surfaces of the shells or panels are firmly andhermetically connected with honeycomb plates 13 by means of an adhesive13b, for instance, of a polyurethane foam developed for this purpose.Instead of an adhesive plastic foam, any other connecting means can beused, for instance, liquid, subsequently polymerizing, sealing plastics.The honeycomb plates 13 are each followed by an air gap 14. Thereafter,a composite group is arranged, said composite group consisting of acomposite sheet (sandwich type) 25a, 25b with, on both sides thereofprovided compressible sealing plates 11, for instance, of plastic foam,felt, asbestos, glass fibers, or rubber. The surfaces of these sealingplates bear preferably vaporproof foils 12, for instance, ofpolyethylene or metal, such as aluminum. Between these parts, at adistance established by an air gap 15, there is provided a singlehoneycomb plate 13, for instance, of metal, plastic, or cardboard. Aplurality of honeycomb plates 13 can also be combined into a sandwich orcomposite unit with the interposition of other plates, such as, sealingplates 11 with foils 12 for instance, by means of adhesive plastic foam.The individual structural element parts and groups of parts are held, ifrequired, at a distance apart of air gaps 14, 15 on the edges offork-shaped supporting means 26 which are arranged movably on supportingledges 27 of a supporting frame. When the air is evacuated from thevacuum housing via pipe 2 with valve 3, it is then removed in the samemanner from all parts of the structural element. Thereupon, the movablesupporting means 26 can be pulled out of the air gaps 14, 15 by means ofelectromagnets 28 and thus said parts of the structural element can movedownwardly one upon the other in the position arranged precisely, forinstance, on stops to their intended final position. Compressing of theparts of the composite structural element can be effected by means ofpressure plate 29 which is arranged on upper structural shell or panel10, for instance, by their weight, or by a compressed-air cylinder withpiston and piston rod 7 which moves in airtight fashion through the lid1a of the vacuum housing. In this way the individual honeycombs arehermetically sealed by the adjoining foam plates 11 being pressedthereinto. If the air is then again let into vacuum housing 1 throughpipe 31, the parts will be further pressed together by the atmosphericpressure and thus all parts of the composite structural element will becombined to form a compact unit. The resulting assembled vacuum housingcan then be removed from the vacuum housing and can be used as desired.

Of course, it is possible also to provide a packing between the edges ofthe shells or panels. In this case the parts of the structural elementcan be placed loosely one on top of the other up to the uppermostcomposite part which is borne by the packing, said packing, in turn,being received or carried at the bottom by supporting means with theformation of an air gap. Since the air in the interior of the structuralelement is of higher pressure than the vacuum in the housing, it flowsalmost completely out. For this purpose special evacuating tubes orhoses can also be arranged above or below the packing or therethroughpreferably provided with valves. The packing can also be appliedsubsequently and the space between it and the core of the structuralelement can additionally be evacuated. Such an element can be used invarious manners as an insert in other correspondingly larger compositestructural elements. It can furthermore be combined in sandwich fashionwith the inner surfaces of larger structural shells or panels of suchlarger composite structural elements, for instance, by means of adhesiveintermediate layers, and particularly by means of adhesive foils oradhesive solid, preferably elastic plastic plates. Insofar as thearrangement of an elastic circumferential packing between the edge partseither of the larger composite structural element or of the smallercomposite structural element to be introduced is necessary, evacuationof the intermediate space can be effected via pipes with valves betweenthe packings and the parts of the structural element.

Provision of the air gaps 14, 15 and/or the arrangement of supportingmeans 26 and electromagnets 28 are necessary in the case of the use oflighter materials, for instance, of aluminum and cardboard honeycombing.The air present in the element parts, except for a very small amount, isforced to the outside during evacuation of the vacuum housing. If acircumferential packing is provided, it may then be necessary to producea connection to the vacuum space 1 via a pipe with valve (see FIG. 1,reference numerals 21, 22). This pipe can also be connected with anevacuating device by passing it through the vacuum housing wall and thuswill render possible evacuation of the composite structural element.Thus in case of lightweight construction, it may be sufficient tointroduce a composite structural element, also with circumferentialpacking, provided with an evacuator pipe and valve mounted into a vacuumhousing in order to evacuate it by elimination of the atmosphericpressure. Thus composite structural elements of heavy individualcomposite elements and groups of elements can be evacuated in this wayvia pipes with valves. When using packings, pressure plate 29 may alsobe dispensed with upon insertion or interspersing of pipes with valves.In all cases the means described permit complete or practically completeevacuation of the air, as required.

The introduction of evacuated smaller structural elements achieves itsimportance through the possibility of imparting to the load bearingsupporting elements contained in the evacuated structural elementespecially if they are formed of composite plates in a single ormultiple bonded arrangement (multisandwich type) or in multiple grouparrangement, a practically unlimited increase in resistance to flexureon the structural shells or panels of the inner smaller structuralelement due to the positive pressure that can be produced in anotherlarger structural element. In this connection the outer structuralshells or panels of at least the smaller structural element can also bedeveloped as load-bearing supporting plates. Under the positive pressurewhich is exerted on their outer surfaces on the one hand, and thecorrespondingly high back pressure which is exerted on their innersides, said shells or panels are supported with corresponding flexuralresistance to receive the loads or other pressures in the direction oftheir plane. For this purpose the outer structural shells or panels ofthe other larger surrounding composite structural element must be ableto take up, with resistance to compression and bending, by suitablestructural development, the excess pressure present in the cavities.This can be effected, for instance, by the provision of intersectingprofiled sheets, and particularly of trapezoidal sheets, the contactingpoints of intersection of which are welded together in multiple layer. Afurther increase in the bending strength of such combined shaped, andparticularly trapezoidal, structural shells and panels can be obtainedin a manner that profiling is effected on composite sheets, consisting,for instance, of metal-plastic-metal (sandwich-shape). Or thetrapezoidally shaped or differently shaped sheets are first of allconnected in this form with solid preferably elastic plastics ofcorresponding shape to form profiled composite sheets (sandwichtype)which are then firmly connected with each other in a singly, or,respectively, multiply intersecting sequence. Such profiled structuralshells or panels can be developed by means of sheets which are closed onall sides to form an airtight and liquid-tight hollow body which, forinstance, can receive plastic foams or any other substances, liquids, orgases serving the purposes of the structural element.

FIG. 3 refers to the advantages of the use of positive pressure in acomposite structural element. FIG. 3 shows diagrammatically incross-sectional view a composite structural element with horizontalarrangement of the individual parts which are inserted in apressure-proof pressure housing 40a, 40b, 40c, 40d and 40e for producingvarious pressure conditions.

The composite structural element consists of outer structural shells orpanels 41 which are made from intercombined, connected trapezoidalsheets 41a, 41b, and of circumferentially extending side walls 42 and 43arranged hermetically sealed thereon and parallel to each other, saidside walls being of lesser width than the distance between thestructural shells or panels. The edges of these side walls are pressedinto circumferential elastic packings 44 and 45 associated therewith. Inthis way the hollow space between the structural shells is closed offelastically with variable air-tightness and imperviousness to vapor. Soas to further assure air-tightness, a third circumferential packing 46can be provided between the edge parts 47 and 48 of the two structuralshells or panels 41.

Within the hollow space, approximately in the center, there is provideda pre-evacuated composite structural element consisting of at least twostructural shells or panels 51, 52, preferably of composite sheets, andof one or more honeycomb plates 53, and load-supportingflexure-resistant composite supporting plates 54 arranged between thelatter. This inner structural element which is pre-evacuated bears onthe outer surfaces of its structural shells or panels a compressiblelayer 55, for instance, of rubber, plastic, or plastic foam. On bothsides of these surfaces 55 there are arranged honeycomb plates 56, forinstance, of steel plate, which before assembling the outer structuralelement have been fastened hermetically to the inner sides of itsstructural shells or panels 41, for instance, by means of adhesivepolyurethane foam 56a or liquid plastic adhesive. Thus the air canpossibly enter the honeycomb plates only along the outer surfaces 55 ofthe inner wall element.

Pipe 57 or the like having a valve 57a is arranged towards the cavity ofthe composite structural element. Via said pipe 57 it is possible tointroduce compressed air through a compressed air device into saidhollow space with any required degree of pressure. The outer structuralshells or panels 41 are pressed by means of said compressed air so farapart against stops (not shown) that between the inner structuralelement and the adjoining honeycomb plates there is formed a fine airgap 58 by which each individual honeycomb is provided with compressedair to the extent contemplated. Thereupon, compressed air of a higherpressure than the positive pressure in the inner structural element isintroduced into the hollow space of the pressure housing 40 by means ofan air compression device via pipe 60 with valve 61. Thereby thestructural shells or panels 41 of the outer element are pressed againsteach other so that the air gaps 58 are closed and the webs or ribs ofthe steel honeycombs 56 are pressed into the compressible layers 55 orplates on the outer surfaces of the structural shells or panels of theinner element in an air-tight and vapor-tight manner. Thus thereprevails within the hollow space of the composite structural element acounter-pressure which corresponds to the positive pressure exerted inthe hollow space of the pressure housing. In order to maintain thisdesired pressure condition, by which the surfaces of the bearingsupporting means 51, 52, 54 are propped or braced, in particular by thehoneycomb plates 53, 56, up to the increased bending strengthcorresponding to the positive pressure, after elimination of thepressure in the pressure housing 40, there are arranged along the narrowsides of the outer structural element means for fixing the minimumdistance between the outer composite structural shells or panels 41 asit is obtained by the external positive pressure. FIG. 3 shows detent orstop means, i.e. engagement means for this purpose, on the structuralshells or panels, such as protruding ledge-shaped parts 66 of the upperstructural shell or panel 41, and other associated parts as well as thedetent or stop ledges 67 with spring-loaded, movable detent or stopelements 68 which can be inserted into the detent or stop strips 67 andwhich snap behind the mating ledges 66 protruding on the upperstructural shell or panel when said structural shells or panels 41 aremoved towards each other. In this way the intended position of thestructural shells with respect to each other which is thus obtained isfixed or locked in position and secured permanently.

In this connection the lower part of the detent or stop strip is inengagement with a rectangular strip-shaped bend 69 of the lower outerstructural shell or panel 41a and thus prevents the detent or stop strip67 from changing the compressed position of the upper structural shellor panel 41 secured by its detent or stop element 68 by engagement afterelimination of the outer positive pressure. In order to prevent lateralforcing away of the detent or stop ledges 67, said ledges are pressedmovably by strong tension springs 70 in the direction towards the detentor stop ledges 66. Of course, means by which it is possible, ifnecessary, to effect a disengagement can also be provided, for instance,by drawing back the detent or stop ledges 67 by means of anelectromagnet. The detent or stop means described are merely onetechnical possibility among many others of achieving the same goal.

FIG. 3a shows schematically in cross section, supplementing FIG. 3, onepossibility of connecting the surfaces of the two structural shells orpanels 41 for instance, by detent or stop means in the end positionimparted to them in the pressure housing, for an unlimited period oftime. For this purpose there are welded onto the inner side of the lowerstructural shell or panel 41 two correspondingly large square pipes 75.Detent or stop elements 76 are inserted against the action ofcompression springs 77 between universal guides 78 in said pipes. Saiddetent or stop elements 76 propel and can be pushed in to an extentwhich is limited by stops. They are provided with backwardly extendingbevels. The distance between the two detent or stop element carriers 75is such that said elements snap and engage into solid body 79 which iswelded to the inside of the opposite structural shell or panel 41 andwhich is provided with incisions 80 corresponding to the triangularshape of the detent or stop elements 76 and their distances apart fromeach other, under spring pressure 77 upon a corresponding change inposition, i.e. reduction of the distance between the structural shellsor panels. Thus they permit further movement up to the end position onlyin direction towards a reduction of the distance between the structuralshells or panels.

Such means which connect the inner surfaces permanently against theinner positive pressure can be arranged in any required number atsuitable places of the surfaces 41. They can also be provided in theform of longer strips. The inserts and supporting plates are to berecessed at the respective places or they are to be provided with slitsor interposed slot spacings.

FIG. 3b shows another embodiment for connecting the composite structuralsurfaces 41 with each other at the minimum distance attained by thepositive pressure. For this purpose bolt 81 is welded onto the innerside of the cavity of the one structural shell or panel 41, said boltpassing through a hermetically closed bore hole 82 in the oppositestructural shell or panel 41 and being adapted to be tightened by nut 83on the outer side thereof. Said tightening must be effected in thepressure space at the maximum pressure established. For this purposescrewing machines 84 connected to be operated electrically from theoutside are arranged precisely with respect to the position of the nuts.In this way the structural shells or panels are connected with eachother at least at a minimum distance apart attained by the positivepressure, i.e. under the condition of the highest pressing tension ofthe supporting means 51, 52, 53 (FIG. 3) with respect to theload-bearing supporting plates 54, so that after releasing the positivepressure air from pressure housing 41 for removal of the structuralelement therefrom, the condition of stress in the evacuated structuralelement remains unchanged.

The described interconnecting means of the outer structural shells orpanels exert an opposing pull or countermove with respect to thecompressive forces which otherwise would cause bulging the outerstructural shells or panels towards the outside and bending in of thesame. These connecting means thus render possible to correspondinglyincrease the bending strength of the inner bearing supporting elements.

Referring to the modified form of the invention shown in FIG. 4, inwhich previously described elements as illustrated in FIG. 1 aredesignated by the same reference numerals, plates 11 may consist e.g.,of solid plastic material, or they may be vertical trapezoid plates 10a,e.g., of metal which are rigidly connected with the adjacent plates.Instead of foils 12, rigid plates, especially metal sheet plates, may beemployed, which, e.g. are welded together with the trapezoidal plate andare preferably universally sealed in an airtight manner. The samestructure as provided for plates 11 and layer 12 is applied to plates 17and layers 18, which are preferably also metal sheets. The packing 20and 20a can be eliminated. The welding of the metal honeycombs 13, e.g.steel honeycombs, together with the adjacent sheet metal plates 12 and18 is carried out, as described, by pressure and resistance and/orelectronic (electric arc) welding, preferably in a vacuum, for whichpurpose the honeycomb plates 13 and the plates 12 and 18 are connectedto opposite poles of a welding machine shown schematically at WM, withcurrent lines thereto, in FIG. 4. The metal sheets 12 and 18 and thejoint elements, as described above are prepared or shaped depending onthe type of welding applied to them. Especially suitable means forholding the evacuated structural element together are tightening screwsor clamp bolts.

These screw means are illustrated more in detail in FIG. 4. Bolt 111v isthreadedly received in sleeve 112 v mounted in the structural element.Said bolt 111v passes throughout the entire structural element and restsor abuts against said element by means of disc or sleeve 113. Adjustingscrew driverlike means 110 engage slit or sleeve 114. Said means 110pass through the wall 1e of the evacuating housing. This device permitsto press together the evacuated structural element in the evacuatinghousing. After removing the compressed evacuated structural element fromsaid housing, its pressure condition, i.e. the vacuum is retained. Suchtightening bolts 111v with their sleeves or nuts 112v can be provided,as required, at any place of the main surfaces of the structural shellsand/or their edge portions. Due thereto the state of stress in thestructural element can be increased additionally and can be maintained.More in particular tensioning of the shells or panels can be carried outin such a manner that they are bent against each other with the deepestdeflection preferably towards the point of intersection of its assumedplane diagonal. As a result thereof the shells or panels are maintainedto an increased extent resistant to bending and breaking whencontinually exposed to load parallel to their surfaces at acorrespondingly increased counter pressure of the supporting and spacingmeans in the cavity or hollow space. In connection therewith theinterior of the cavity or hollow space can be further equipped, ifrequired, more or less with further supporting means. Or it may beprovided with only a few spacing means, preferably in combination withthe tightening screw or clamp bolts.

Due to the tension to which the shell is exposed and to the vacuum thereis achieved a high sound insulation which can further be improved byadditional means provided in the hollow space or cavity and tensionedwith their inherent frequency. The highly reflecting foils and/or sheetscan have a sound insulating capacity not only due to their tension butthey also are capable of reducing very considerably transmission of heatenergy due to their property as reflecting means. Instead ofcompressible insert or spacer elements, pressure springs for securingairgaps 14 and 15 may, for instance, be inserted. The valves 21,22 aredispensed with in the FIG. 4 form of the invention in which the packing20 is eliminated. The welding machines may be arranged outside thewelding space, and the feeder cable may be guided through the spacewalls in an airtight manner into the evacuating housing.

The modification described with reference to FIG. 4, according to whichthe plastic material foam plates 11 were replaced, e.g., by plasticmaterial plates or shaped metal plates, e.g. trapezoid plates, appliesalso to FIG. 2; this applies also to a multiple, preferably crosswisearrangement with airtightly sealed metal sheets inserted by welding andfor transverse subdivisions which form airtight chambers. In place offoils 12 metal sheet plates or composite plates may be provided.Furthermore, the honeycomb plates or the like are connected, extendingin a direction opposite to the adjacent plates, to the poles of thewelding machines, and then the welding is carried out under the pressureof plate 29. Forks 26 are made of, or covered with, insulating material.

The pressure plate 29 may also be constructed as electromagnet plate andsupport magnetically at least the uppermost portion of the constructionelement. It may also be arranged resiliently so as to exert a specificelastic prespecified welding pressure.

Referring to the FIG. 5 modification, in which previously describedelements are illustrated by the same reference numerals, the internalconstruction element 52, 53, 54, the same may be modified as explainedabove with respect to the modifications relating to FIGS. 1 and 2. Theinternal evacuated construction element may be an element rigidly weldedto a unit and consisting e.g. of steel honeycombs, steel cover sheetswith shaped plates, inserted by welding between such cover sheets, e.g.,corrugated plates, trapezoid plates, especially with crosswise sequencewith intermediate plates and transverse subdivisions for the formationof airtight cells or chambers. The trapezoid building shells 41a and 41bmay also be constructed with intermediate plates and chambersubdivisions in an airtight manner, and with vacuum. The weldingtogether with the honeycombs 56 provided with excess pressure can becarried out as described above. The compressed air pipe 57 can beremoved at any time. The sealing 44 is provided with small slit. Whenthe pipe is being removed, the slit closes in a airtight manner.

In the FIG. 5 form of the invention, the shells or panels 41 areconnected to each other at a minimum distance attained by the positivepressure as described by means of a bolt 120 which is secured at one endto nut 121 secured to one panel and which extends at its other endthrough the other panel 41, through disc 123 for the desired tighteningby nut 122 which engages the exposed end of the bolt.

Basically, in all cases suction and pressure pipes can be arranged insuch a way that they are detachable through slits in the sealings orthrough bipartite sealings and they can be removed again, whereafter theslits close in an airtight manner under the pressure exerted upon thesealings.

The invention can be made use of in a multi-shell or multi-panelcomposite element in such a manner that the outer structural shells orpanels are fixed in position and the inner intermediate shells or panelsare arranged movable. Every two movable inner intermediate structuralshells or panels define a cavity into which compressed air isintroduced. In this way the distance between the two displaceablestructural shells or panels is increased and the pressure on the cavityinserts of the inner structural element which are placed under tension,is correspondingly increased. In order to maintain this pressure, afterthe intended maximum distance of said two movable structural shells orpanels has been obtained, a rapidly hardening liquid structural materialcan be introduced into said pressure space under an even greaterpressure. In order to be able to introduce the compressed air which isto be displaced by this liquid structural material without loss ofpressure, an outlet valve can be arranged in the upper air-space part,said valve making it possible that when a predetermined pressure isexceeded, the compressed air is allowed to flow out as from saidpredetermined degree of pressure. In this way it is also possiblepermanently to fix the predetermined optimum pressure-tension condition.

At the same time it is possible to span with great forces ceiling andfloor parts (or upper and lower parts) of structural elements, forinstance, for bridges with such displaceable outer shells or panels andnon-displaceable outer shells or panels facing each other in a pressurecavity of the structural element. For this purpose a movable structuralshell or panel can then be arranged against following pressure means andload-bearing supporting means on each of the two non-displaceable outershells or panels at a slight distance so as to form a pressure cavity.This arrangement can be effected, for instance, for bridges in recurringsequence as necessary for increased tension or span of upper and lowerpart.

It is also conceivable to provide in a pressure cavity of a structuralelement, for subdividing thereof, a plurality of air hoses withindividual valves to establish the intended pressure in them. Upondamage to the pressure cavity, the undamaged hoses continue to exerttheir pressure action. Extremely high compressive stresses can beexerted by applying a corresponding positive pressure within such aconstructed structural element having non-shiftable outer structuralshells at least on both sides via one or more hermetically arrangedstructural shells or panels arranged shiftable in the inside, on theload-bearing supporting means associated with them. The connecting uppercover or ceiling part and lower bottom or floor parts can be tautlytensioned in this manner.

The composite structural element forms a single composite unit from astatic standpoint For this reason, the connections between the core andthe outer plates and at least the intermediate shells or panels must beso firm that the shear stresses transmitted to the boundary surfaces aretaken up by the outer plates or intermediate shells or panels withoutsaid plates and panels becoming loose. For this purpose the outer platesand/or shells or panels are to be constructed with a sufficient minimumstrength as well as a sufficient minimum flexural strength.

The load-bearing supporting plates can be placed under compressivestress in various manners. Thus the compressive stress can be alsoproduced by liquids which are placed under compressive stress. Water ofhigh pressure can be introduced into a hollow chamber of the structuralelement and a vacuum can be present in an adjoining hollow chamber, orwater with the normal pressure determined by the atmospheric pressurecan be introduced. Such pressures can be exerted also purelymechanically, for instance, by lever actions against a plate or shell(panel) to be displaced, or, for instance, via a compressed air cylinderwith piston rods against a displaceable shell (panel), or, as describedabove, by tightening screws or clamp bolts.

It is sufficient to effect this pressure action only from one side andto have the counter-pressure which is exerted via a stationary shell(panel) on the load-bearing support, act on the other surface of theload-bearing supporting means. Nevertheless it is advantageous forreasons of safety to have the pressure action exerted from both sidesshould the pressing force fail to act on one of the two shells (panels).To achieve this result, it is advisable to keep as small as possible thedistance between the movable shell (panel) exerting the pressing forceand a pressure-resistant stationary wall associated with it. Should thena failure occur, the required pressure will be produced by the othermovable displaceable shell (panel) and the full bending strength of theload-bearing supporting means will be retained by the opposite force ofthe stationary wall, without any reduction in force. It is furthermoreadvisable to fill the hollow space between said shells or panels withhoneycomb plates up to a minimum gap of less than one millimeter.

The use of honeycomb plates for use in the pressing step differs fromthe use of flat plates. In the case of flat plates, the pressingpressure is distributed uniformly over the entire area of the pressingplate. In the case of a honeycomb plate, however, only the very narrowribs of the honeycombs transmit the entire pressure. These ribs as arule can take up less than 1% of the surface to be pressed. This meansthat the total pressure which is exerted on the honeycomb plate istransmitted by these ribs with more than hundred times the force to thelines of the surfaces to be pressed which are contacted by them. Itfollows that a corresponding stress structure results from said pressinglines. The free space between the ribs of the honeycombs is subjected,on the other hand, to flexural forces.

Therefore, the honeycomb surfaces must be in a specific, size ratio withrespect to the bending strength of the plate to be supported, on the onehand, and to the load borne by the load-bearing supporting plate, on theother hand, in order to prevent bulging or bending in or kinking of theload-bearing supporting plate. It is advantageous to provide for optimumwidths of the honeycombs with a relatively small size of the honeycombribs in order to increase as much as possible concentration of theenergy of the respective lines corresponding to the honeycomb structure.In combination with the relatively small height of the honeycomb ribsthey should also be made as resistant as possible to bending, forinstance, by the use of steel sheets.

The honeycombs in the stress cavity which receives the load-bearingsupports can be filled, for instance, with plastic foam for reasons ofinsulation as well as to support the honeycomb ribs against bending inor kinking. In this connection, however, said fillings should not rest,or they should rest without pressure, against the surfaces of thesupporting plates.

Instead of honeycombs, it is also possible to use grids which aresubdivided in the corresponding optimum grid fields and which haveknife-thin edges at the place of contact with the load-bearingsupporting plates. On the other hand, it is advantageous to provide aflat shape on the pressing side.

When using the composite structural elements in the building of housesthe construction of multi-shell (multi-panel) composite structuralelements, and at least a three-shell (three-panel) structural element isof advantage. The third shell (panel) of such an element at the sametime forms the inner wall of a room of the building. A hollow spacewhich in particular must satisfy the fire protection requirements shouldbe provided between said third shell (panel) and the centralintermediate structural shell (panel) arranged in front thereof.

In order to exclude collection of water of condensation as a result ofthe penetration of water vapor, the hollow space must be closed off invapor-tight fashion on all sides. This can be done in the manner thatall non-metallic wall parts of the hollow sapce are covered, forinstance, with aluminum foil or a vapor-impervious polyethylene plasticfoil. In addition thereto there is the further problem of preventing thestresses on the hollow space walls resulting from variations in pressurecaused by temperature variations in the hollow space. For this purposethe invention contemplates connecting the hollow space by a pipe withthe atmosphere. In this way the result is obtained that the pressure inthe hollow space always agrees with the variations of pressure in theatmosphere. In order to prevent penetration of atmospheric moisture intothe hollow space, the pipe can be hermetically provided towards thehollow space with a flexible air bag formed, for instance, of plasticfoil. This air bag can be provided with spring spreading means by whicha necessary minimum of its fillable volume is filled with outer air. Ifthe pressure of the atmosphere increases, then this air bag isadditionally filled with air, while if the pressure of the atmosphericdecreases, air is given off to the outside by the air bag. In this waythe hollow space remains closed in vaportight fashion from the outsidewithout it being possible for stresses to occur.

Particularly when the inner wall of the room consists of a thin shell orpanel of structural material, for instance, a plaster wall or a ceramicwall, it is necessary to support said wall. This can be done by a sheetmetal wall which at the same time forms the structural shell or paneltowards the inner cavity of the structural element. Such a sheet metalshell or panel can hermetically close off a hollow space intrapezoid-like fashion, if necessary; by two intersecting trapezoidalsheets or panels and can be constructed in the other direction so as toenclose the plaster wall on all sides. The hollow spaces resulting fromthe trapezoidal profiles towards the plaster wall can also beconstructed in an air-tight and liquid-tight fashion and can be filledwith fire-retarding materials, for instance, with a suitable form ofasbestos. Other agents, for instance, rock wool, glass, fibers, and thelike can also be used for this purpose. Above these trapezoidalintermediate space and the plaster wall there is arranged awater-bearing pipe with thermostatically controlled openings directedtowards the rear surface of the plaster wall. If the heat of the firereaches in case of a fire the thermostats at a predeterminedtemperature, for instance, through small openings in the upper part ofthe plaster wall, then the water pours out against the rear of theplaster wall and at the same time enters the said cavities which areformed by the trapezoidal depressions. Thereby it permeates the asbestosfilling and/or the other solid fillings, for instance, rock wool, whichare provided therein, and wets the absorptive rear side of the plasterwall.

The latter can be provided with bore holes through which the waterpasses to the front side and trickles down in the form of a curtain ofwater. In this way the plaster wall will be cooled continuously and theheat of the fire will be reduced by the conversion of the water intosteam. The steam displaces to an extent corresponding to its generationthe oxygen-containing air and can thus increasingly exert anextinguishing action on the source of the fire. A water pipe havingopenings directed towards the front surface of the plaster wall andcontrolled by thermostats can also be provided on the front surface ofthe plaster wall. Such a water curtain prevents the heat of the firepenetrating via the plaster wall into the composite structural element.In this way considerable conventional fire-protection structuralmeasures can be eliminated and saved. A further increased fireprotection can be effected by applying to the front plaster wall acarbonate layer and the water, before it flows into the perforated pipesforming the water curtain, is conducted through a container in whichthere are contained dissolved or soluble agents which react chemicallywith the carbonates on the plaster wall so as to liberate carbon dioxidetherefrom. Providing such containers of the aforementioned pipes ispossible above the customarily suspended ceilings without great expense.The carbon dioxide displaces the oxygen-containing air and extinguishesthe flames.

The liquid-proof depressions in the trapezoidal structural shells orpanels can be filled with hot water from a heating system for roomheating or cooling. The fire protection described can be obtained in thesame manner through openings towards the plaster wall.

If a flat structural shell or panel is used, a correspondingly thickerplaster wall can be provided on its rear, for instance, with vertical,undulated profilings to form hollow spaces. This rear side, forinstance, can have pasted on a plastic foil, such as a polyethylenefoil, so as to achieve a water-proof and steam-proof closure. In case offire, this foil melts at about 150° C. and, when molten, allows thewater to penetrate into the absorbent plaster wall. All the otherprotective measures described hereinabove can also be provided.

The supporting elements produced in accordance with the presentinvention may be of any suitable shape.

Such supports can consist, for instance, of longitudinally slit pipeswhich are arranged concentrically in an unslit pipe. The pipes or,respectively, the pipe intermediate spaces can be closed at their endsin an air-tight and/or vapor-tight manner and can be sealed elastically.Thereby the sealings are effected in such a manner that changes in thediameter of the concentrically arranged slit pipes which occur when thepipes are under pressure, are taken into account and the seals are notendangered thereby. Furthermore, all seals can be reinforced and securedby elastic plastic foams. The inner equipment of the pipes for theirconstruction as supports is in principle, aside from their round shape,the same as in the case of the square composite structural element. Inorder to effect compressive stresses, a change of the slotted pipes bychanging their diameter is necessary in the same way as a change inposition of the structural shells or panels is required in the case ofthe structural elements. The longitudinal slits in the pipes areresponsible for said change. Due to said slits a change in the diameterof the individual slit pipes takes place under the pressure ofintermediately arranged pressure means, for instance, by means ofcompressed air or liquid under pressure on the inside or the outside ofthe intermediate load-bearing supporting pipe.

First of all it is necessary to seal the slits elastically so as toprevent the compressed air penetrating into adjacent concentric spaces.Such seals can be effected, for instance, by elastic packing inserts inthe slit perpendicular to the pipe surfaces. If a higher pressure isexerted on the slit pipe in the direction from the outside towards theinside, the edges of the slits will be pressed against the elasticpacking and thus will reinforce the seal. The entire region of theslitting of a pipe is supported and sealed with elastic sealing means.

The edges of the slits themselves can be deformed. Thus, they can bepressed flat for sealing, for instance, by rectangular bending, againstthe sealing means provided between them. The bendings can also beconnected with bolts which pass through the packings just as in the caseof the structural element. They can also be bent by 180° C. The bend canbe provided with elastic sealing means and can be in engagement witheach other.

The intermediate spaces between every two pipes can, for instance, beformed as follows:

Air-tight sealing strips, for instance, rubber strips can be bonded overthe pipe slits on one or both sides so as to cover the slit. Thereuponpressing means, in particular, for instance, circular honeycomb plates,preferably also slit, consisting, for instance, of metal, plastic, orcardboard, can be arranged in one or more layers so as to fill up theintermediate space approximately. It is advantageous to use honeycombplates having relatively low ribs in order to achieve the best possibleflexural strength of the ribs. Otherwise all that has already beenstated with regard to the honeycomb plates, applies to the structuralelements. In the case of a plurality of honeycomb plates, for instance,lighter slit pipes of the same or different material can be arrangedbehind every honeycomb plate in order to air-tightly subdivide the spaceand to transmit pressure to the next following honeycomb plate. Forstatic reasons, it is necessary to connect all inserts firmly to eachother in order to be able to expose them to tension, compression, andshear load.

The spaces between two concentric pipes correspond in their function tothe hollow spaces of the composite structural element. As in that case,the adjoining structural shells or panels are partly nondisplaceable inposition and partly displaceable. The slit pipes correspond to thedisplaceable structural shells or panels of the structural element. Thusnumerous different possible combinations are available.

All the spaces can be provided with pipelines with valves so as to applyin each case in accordance with the desired combination, for instance, avacuum to the one hermetically closed space and pressure to the twoadjacent spaces. In this example, the two pipes which limit the vacuumspace are slit and these slit pipes are pressed together or,respectively, reduced in diameter by the compressed air in the adjacentspaces. In this manner there is achieved a change in position by whichincreased resistance to bending and thus increased load-bearing capacityis imparted thereto by pressure and counter-pressure from the inside.Instead of producing a vacuum in the intermediate space in this example,atmospheric pressure can, for instance, prevail therein and the excesspressure in the adjacent spaces can be maintained one atmosphere higher,whereby the same supporting effect is obtained.

For instance, all pipes, with the exception of the outer pipe, can beslit pipes which are concentrically arranged one within the other withintermediate spaces. In this example, compressed air can be introducedinto the cylindrical space to the innermost slit pipe. In this way thediameter of this pipe is increased, whereby a corresponding pressure isexerted on the pressing means, for instance, on circular honeycombplates (which are also slit) in the direction towards the outer pipeover all intermediate slit pipes and pressing plates. The outer pipe,for instance, as a solid pipe, must take up the entire pressure which isexerted on its inner wall and must be able to respond ascounter-pressure. For this purpose, pressure-resistant rings can beplaced at suitable distances around the outer pipe. In the latter case,the outer pipe can appropriately be constructed as slit pipe.

According to another example, the excess pressure can originate from theintermediate space which is defined by the outer pipe, on the one hand,and from the cylindrical cavity of the innermost slit pipe, on the otherhand, so that all pipes lying concentrically therebetween are supportedin flexure-resistant fashion from both sides by the pressing means.

By an annular reinforcement of the outermost pipe, it represents also aload-bearing supporting pipe which is propped or braced with increasedresistance to bending from the inside, on the one hand, by the pressingmeans acting thereon and, on the other hand, by the counter-pressureoriginating from the rings. The rings can also be split, bent, andprovided with tightening screws or clamp bolts.

In the same way as in the case of a structural element, it is ofadvantage to hermetically seal at least each of the honeycombs,chambers, or the like of the pressing means in order not to impair theflexural strength of the pipe supports in case one pipe is damaged. Toachieve this result, the procedure is the same as described hereinabovewith respect to the composite structural elements.

The grid-like pressing by means of the honeycomb ribs produces the sameresult of concentrating the pressing forces on the lines on contact. Itfollows that such pipe supports differ only in shape from therectangular composite structural elements or supports. The pipes can beconstructed in sandwich fashion in order to increase their resistance tobending. In place of circular honeycombs, there can be arrangedcorrugated plates as pressing means in the intermediate spaces. Saidcorrugated plates are preferably subdivided in transverse direction intoa large number of small compartments each of which can be hermeticallysealed off. The connecting means and other means for maintaining anoptimum supporting pressure produced by temporary excess pressure can beemployed in a fashion similar to that described with respect to thestructural elements. Furthermore, for instance, a predetermined excesspressure in the cylindrical hollow space defined by the innermost slitpipe can be maintained permanently and thus without change by theintroduction of a hardenable liquid structural material, for instance,of concrete. The compressed air should also preferably be dehumidifiedby means of drying agents to such an extent that water of condensationcannot form in the hollow spaces of the pipes.

Supplementing the above statements, it is pointed out that thehoneycombs or grid plates, depending on requirements, can be constructedin a specific way so that their material strength and bending resistanceare increased. Thus, e.g., in the case of high compression or loadstresses, it is advantageous for the purpose of increasing the strengthand achieving a high bending resistance, to manufacture grid plates frompieces of square pipes with inserted plane intermediate bands (extendinghorizontally or vertically) to which the square pipe pieces are weldedand/or cemented. The square openings may be jointed to a rigid compoundunit, toward both sides, with adjacent building plates, as describedabove, by welding. Such compound plates present an extremely increasablestrength and bending resistance due to the square shape and the weldingtogether of all parts, as well as the selection of the materials andmaterial strength. When such a plate is subjected, as a core plate withrelation to supporting building shells or compound building shells, totension by means of a pressure exerted from the outside, not only thebuilding plates abutting to the said plate present an increased bendingresistance but the plate itself is given a high supporting capacity(bearing strength). The material thicknesses of the square pipes mustcorrespond to requirements, and likewise the intermediate bandsconnected with the said square pipes horizontally or vertically.

As already mentioned, it is also feasible to provide plastic materialplates for the manufacture of core plates with chambers, cells, or thelike. Thus, e.g. metal honeycombs or grid plates can be heated,preferably by electric means, to a suitable temperature and can bepressed by means of pressure plates against plastic plates arranged atboth sides of the honeycomb plates. In this process, the metalhoneycombs penetrate the cover plates or building plates of plasticmaterial, due to their plastic melting temperature, down to the depthrequired in each case, by the prespecified pressure of the pressureplates. By this process the individual chambers, cells, honeycombs, orthe like, are sealed against each other in an airtight manner, and e.g.,a vacuum is maintained therein.

For producing a vacuum inside a construction element numerouspossibilities exist. The screws by which the edge portions of thebuilding shells, with insertion of elastic sealings, are connected, arefirst screwed in only to the point where an airtight sealing takesplace. Thus they can maintain the edge portions of rigidly shapedbuilding shells and thereby the larger distance thereof from each otherfor the purpose of air evacuation. After the evacuation has been carriedout, the screws are screwed inward by screwing machines to theirterminal positions.

It is also possible to proceed in such a way that, as a deviceadditional to the edge portions of the building plates and also, e.g.,of an inserted building plate, which like the external building platesis arranged at the screws with sealings, on both sides of each edgeportion, nuts or check nuts are provided by means of which the positionof the edge portions at the required distances from each other ismaintained by changing the position of these nuts with respect to eachother. The sealings seal in this process all parts with respect to eachother toward the outside in an airtight manner. Through slits in thesealings suction pipes may be introduced by means of which the air isevacuated by way of valves or stopcocks by means of a suction pump, fromthe construction element. Then the suction pipes are pulled out from theslits, in which process the slits are sealed in an airtight manner underthe pressure which is exerted upon the sealings. The screws or nuts canthen mechanically be brought back to their terminal position bycorresponding tightening.

In a similar manner screws may also be arranged inside the constructionelement between the building shells. The end of such a screw is weldedto the inside, e.g., of the front wall building shell. A screw sleevewith internal threads engages the external threads thereof. This screwsleeve bears a screwhead which is provided at the external surface ofthe other external shell for the purpose of actuating the screw sleeve.At the end of the screw sleeve, e.g., a disc is fastened which, e.g.bears an elastic spacer toward a middle building shell or abuts directlyagainst the middle building shell.

A second disc, having an elastic spacer arranged on the sleeve withrespect to the disc may be provided. When the screwhead is actuated thedistance between the building shells can thus be increased or decreased.This makes it possible to separate the three building shells from eachother to such an extent that between the honeycomb plates and thebuilding shells any amount of free space for evacuating the air in thebuilding element exists. After the evacuation the edge screws as well asthe sleeve screws arranged with relation to the surfaces are tightened,and thus the honeycomb plates, wherein, e.g., a vacuum exists, aresealed against each other in an airtight manner.

The evacuation of the air can also be made possible in such a mannerthat the atmospheric air pressure exerted upon the external buildingshells is lifted off therefrom. For this purpose, box-type buildingshells with rigid, stiffened surfaces, resisting the atmosphericpressure, and sealings, extending circularly along the periphery, arearranged as an additional detachable device, at the screws with whichthe building shells are connected. Then the additional hollow spacesthus formed are evacuated, in which process the atmospheric pressurecannot affect the construction element but is absorbed by the edgescrews that extend circularly around the construction element. Thehollow of the building element is then evacuated, preferably by means ofsuction pipes, detachably inserted in slits or the like, with valves andstopcocks, whereafter the additional external box-shaped building shellsare, through pipes and stopcocks provided thereon, again filled withair, and the atmospheric pressure can act upon the external buildingshells of the construction element. All elements are pressed together bythe pressure and possibly by adhesive layers applied shortly before thisprocess, to a rigid compound unit which is capable of offering therequired resistance to the prespecifiable pushing forces. Then thesuction pipes are removed from the edge sealings. The slits or the likein the sealings are closed in an airtight manner by the pressure whichprevails in the sealings. These slits can, in addition, be hermeticallycemented from the outside, e.g., with adhesive steamtight foils, e.g.,aluminum foils or polyethylene foils.

The invention makes it possible to bear high loads, with a very smalluse of material, in a load-bearing manner up to the limit of materialstrength.

I claim:
 1. A method for the manufacture of a load-bearing structuralelement comprising the steps of:(a) positioning outer structural shellassemblies made at least partially from sound insulating material in ahousing in spaced apart arrangement so as to provide a hollow space; (b)inserting a pair of honeycomb plates in the hollow space between saidshell assemblies in spaced relation thereto and spaced from each other;(c) positioning a central load-bearing support assembly made at leastpartially from sound insulating material between said honeycomb plates,with said central support assembly being spaced from said honeycombplates so as to provide gaps therebetween; (d) pressing said outerstructural shell assemblies inwardly so as to press the edges of saidhoneycomb plates firmly against the surfaces of both the outerstructural shell assemblies and the adjacent surfaces of the centralload-bearing support assembly, and (e) applying a welding current tosaid honeycomb plates and the adjacent outer shell assemblies andcentral support assembly so as to rigidly interconnect said honeycombplates thereto, thereby to provide a load-bearing, flexure-resistantcomposite building element which is both sound and heat insulating. 2.The method of claim 1 further including the step of evacuating thehollow space before said honeycomb plates are firmly pressed and welded.3. The method of claim 2 wherein said evacuation is effected byinserting the structural elements in an air tight vacuum housing, andevacuating the air from said housing and thus from the structuralelements positioned therein.
 4. The method of claim 1 further includingthe step of applying pressure to said hollow space, and wherein thepressure applied during the step of pressing said honeycomb platesagainst said outer structural shell assemblies and said centralload-bearing support assembly exceeds the pressure in the hollow spaceof the structural element.
 5. The method of manufacturing a load-bearingstructural element comprising the steps of:(a) assembling in a housingthe components of the structural element, including outer shellassemblies, an intermediate load-bearing composite group, cellular websdisposed between and spaced from said shell assemblies and saidcomposite group, and compressible packing members connected to andextending between said shell assemblies to form therewith a cavity forreceiving said composite group and said cellular webs; (b) creating thedesired pressure conditions within said housing and within said cellularwebs which are in flow communication with the interior of said housing;(c) compressing said assembled components by applying inwardly directed,contact pressure on the outer surfaces of said shell assemblies formoving the same toward each other, the inner surfaces of said shellassemblies and the surfaces of said composite group engaging theadjacent surfaces of said cellular webs thereby vapor-tightly sealingthe webs into individual cells at the pressure levels originallyestablished in said housing, and (d) removing said sealed element fromsaid housing.
 6. A housing for manufacturing a load-bearing structuralassembly, comprising:(a) a plurality of interconnected wall memberswhich form a closed and sealed chamber for receiving said structuralassembly; (b) means for admitting a gaseous medium under pressure to orevacuating a gaseous medium from said chamber thereby to provide withinsaid chamber a predetermined pressure condition; (c) movable pressureplate means disposed within said chamber; (d) means for moving saidpressure plate means so as to compress said structural assembly whilesaid pressure condition is maintained in said chamber, and (e)electromagnet means positioned in said housing, the ends of saidelectromagnet means in an extended position being positioned closelyadjacent supporting and spacing means adapted to space parts of saidstructural assembly from each other during evacuation of said chamber,and electromagnet means when activated and withdrawn serving to removesaid supporting and spacing means so as to permit said structuralassembly to be compressed by said movable pressure plate means.